Merge 4f12032 into 3e6a289

diffsims/generators/rotation_list_generators.py

@@ -31,6 +31,7 @@
     get_uv_sphere_mesh_vertices,
     get_cube_mesh_vertices,
     get_icosahedral_mesh_vertices,
+    get_random_sphere_vertices,
     beam_directions_grid_to_euler,
 )
 
@@ -186,8 +187,8 @@ def get_beam_directions_grid(crystal_system, resolution, mesh="spherified_cube_c
     mesh : str
         Type of meshing of the sphere that defines how the grid is
         created. Options are: uv_sphere, normalized_cube,
-        spherified_cube_corner (default), spherified_cube_edge, and
-        icosahedral.
+        spherified_cube_corner (default), spherified_cube_edge,
+        icosahedral, random.
 
     Returns
     -------
@@ -216,13 +217,14 @@ def get_beam_directions_grid(crystal_system, resolution, mesh="spherified_cube_c
             points_in_cartesians = get_cube_mesh_vertices(
                 resolution, grid_type="spherified_edge"
             )
-
+    elif mesh == "random":
+        points_in_cartesians = get_random_sphere_vertices(resolution)
     else:
         raise NotImplementedError(
             f"The mesh {mesh} is not recognized. "
             f"Please use: uv_sphere, normalized_cube, "
             f"spherified_cube_edge, "
-            f"spherified_cube_corner, icosahedral"
+            f"spherified_cube_corner, icosahedral, random"
         )
 
     if crystal_system == "triclinic":

diffsims/generators/sphere_mesh_generators.py

@@ -442,6 +442,40 @@ def get_icosahedral_mesh_vertices(resolution):
     return vertices
 
 
+def get_random_sphere_vertices(resolution,seed=None):
+    """
+    Create a mesh that randomly samples the surface of a sphere
+
+    Parameters
+    ----------
+    resolution : float
+        The expected mean angle between nearest neighbor
+        grid points in degrees.
+    seed : int, optional
+        passed to np.random.default_rng(), defaults to None which 
+        will give a "new" random result each time
+
+    Returns
+    -------
+    points_in_cartesian : numpy.ndarray (N,3)
+        Rows are x, y, z where z is the 001 pole direction
+
+    References
+    ----------
+    https://mathworld.wolfram.com/SpherePointPicking.html
+    """
+    # convert resolution in degrees to number of points
+    number = int(1/(4*np.pi)*(360/resolution)**2)
+    if seed is not None:
+        rng =np.random.default_rng(seed=seed)
+    else:
+        rng = np.random.default_rng()
+
+    xyz = rng.normal(size=(number, 3))
+    xyz = (xyz.T/np.linalg.norm(xyz, axis=1)).T
+    return xyz
+
+
 def beam_directions_grid_to_euler(vectors):
     """
     Convert list of vectors representing zones to a list of Euler angles

diffsims/tests/test_generators/test_rotation_list_generator.py

@@ -57,6 +57,7 @@ def test_get_grid_around_beam_direction():
         "spherified_cube_edge",
         "spherified_cube_corner",
         "icosahedral",
+        "random",
     ],
 )
 @pytest.mark.parametrize(
@@ -74,6 +75,7 @@ def test_get_grid_around_beam_direction():
 def test_get_beam_directions_grid(crystal_system, mesh):
     grid = get_beam_directions_grid(crystal_system, 5, mesh=mesh)
 
+
 @pytest.mark.xfail()
 def test_invalid_mesh_beam_directions():
     _ = get_beam_directions_grid("cubic", 10, mesh="invalid")

diffsims/tests/test_generators/test_sphere_mesh_generators.py

@@ -22,6 +22,7 @@
     get_uv_sphere_mesh_vertices,
     get_cube_mesh_vertices,
     get_icosahedral_mesh_vertices,
+    get_random_sphere_vertices,
     beam_directions_grid_to_euler,
     _normalize_vectors,
     _get_first_nearest_neighbors,
@@ -30,6 +31,12 @@
 )
 
 
+def test_random_sphere_mesh():
+    grid = get_random_sphere_vertices(1)
+    assert grid.shape[0] == 10313
+    assert grid.shape[1] == 3
+
+
 def test_get_uv_sphere_mesh_vertices():
     grid = get_uv_sphere_mesh_vertices(10)
     np.testing.assert_almost_equal(np.sum(grid), 0)